Adaptive Cyclic Shift Allocation for Uplink Reference Signals
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Solution Overview
Problem
In uplink communication systems, the existing methods for generating reference signals do not account for dynamically changing delay spreads of mobile users, leading to inefficient resource allocation and reduced availability of orthogonal reference signals, which hampers accurate channel estimation and scheduling.
Innovation Solution
The proposed solution dynamically allocates cyclic shift values for reference signals based on estimated channel delay spreads of user equipment, allowing each user equipment to form its reference signal by applying a tailored cyclic shift to a Constant-Amplitude-Zero-Auto Correlation (CAZAC) sequence, thereby optimizing resource utilization and increasing the number of available orthogonal reference signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If fixed cyclic shift values are used for reference signals, then orthogonal reference signals can be generated, but the number of available orthogonal reference signals is limited and resource allocation is inefficient
Solution Approach 1:
The patent applies dynamics by making the cyclic shift value adaptive rather than fixed. The cyclic shift is dynamically adjusted based on the delay spread channel parameter, allowing the system to optimize reference signal generation for different channel conditions. This resolves the contradiction by enabling more orthogonal reference signals to be generated adaptively without requiring a completely new complex generation mechanism.
Solution Approach 2:
The patent changes the parameter of cyclic shift value from a fixed constant to a dynamic parameter that varies with channel delay spread. By modifying this key parameter based on channel conditions, the system can generate more orthogonal reference signals efficiently. This parameter change approach allows the system to adapt to different scenarios without increasing fundamental system complexity.
2Productivity
If adaptive cyclic shift values are allocated based on delay spread, then multiplexing capacity is enhanced, but overhead for transmitting cyclic shift information increases
Solution Approach 1:
The patent makes the downlink grant message multi-functional by incorporating both resource allocation information and cyclic shift indication in the same message structure. This allows the system to transmit adaptive cyclic shift values without requiring separate dedicated signaling channels, thereby enhancing multiplexing capacity while minimizing additional overhead.
Solution Approach 2:
The patent merges the cyclic shift indication with the existing downlink grant message that is already transmitted for resource allocation. By combining these two functions into a single message, the system avoids transmitting separate cyclic shift information, thus reducing overhead while still enabling adaptive cyclic shift allocation to improve multiplexing capacity.
3Measurement precision
If existing reference signal generation methods are used, then implementation is simple, but accurate channel estimation and scheduling are hampered due to inefficient resource allocation
Solution Approach 1:
The patent implements feedback by using the delay spread channel parameter (obtained from channel estimation) to determine the cyclic shift value for reference signals. This closed-loop approach where channel conditions inform the reference signal generation enables more accurate channel estimation and better resource allocation, resolving the contradiction between measurement precision and productivity.
Data Source
AI summary
A method and apparatus for defining transmission parameters of user equipment reference signals. The method includes estimating channel delay spreads of a plurality of user equipments scheduled for transmission at a particular transmission time period or sub-frame in an uplink for communication with a NodeB, and allocating transmission parameters to each scheduled user equipment of the plurality of user equipments in accordance to the delay spreads of the plurality of user equipments scheduled for transmission in the particular time period or sub-frame, wherein the parameters comprises a cyclic shift allocated to each m-th user equipment equal to the sum of a delay spread and a timing uncertainty of each of the previous m-1 user equipments.